Existing magneto-caloric material heat generators utilize the magneto-caloric properties of certain materials such as gadolinium or certain alloys that have the ability to heat up when subjected to a magnetic field and cool down to a lower temperature than their initial temperature when the magnetic field disappears or weakens. Actually, as they pass before the magnetic field, the magnetic moments of the magneto-caloric material become aligned, causing a rearrangement of the atoms that generate the heating of the magneto-caloric material. When they are outside the magnetic field or if the magnetic field becomes weaker, the process is reversed and the magneto-caloric material cools down to a temperature lower than its initial temperature.
A team of U.S. researchers has developed a working prototype of a magneto-caloric material heat generator comprising a disc formed of thermal sectors containing a magneto-caloric material in the form of a gadolinium alloy. This disc is guided in continuous rotation on its axis so as to cause its thermal sectors to pass inside and outside a magnetic field created by a fixed permanent magnet overlapping a portion of the disc. Opposite the permanent magnet, the disc passes through a thermal transfer block comprising two heat-transmitting fluid circuits, one of which is designed to transport calories and the other to transport frigories generated by the thermal sectors alternately subjected to the presence and absence of the magnetic field. The thermal transfer block comprises orifices opening onto the rotating disc and allowing contact between the heat-transmitting fluid and the rotating thermal sectors. Despite the existence of turning seals, it is very difficult to form a tight seal between the thermal sectors and the thermal transfer block without penalizing the global output of the thermal generator. Moreover, each time a thermal sector is either subjected or not subjected to the magnetic field and therefore heated or cooled, it is necessary to switch the inlets and outlets corresponding to the hot circuit or the cold circuit. As a result, this device is complex, unreliable, limited in output and unsatisfactory.
Publication WO-A-03/050456 describes a heat generator essentially similar to the preceding one and using two permanent magnets. This heat generator comprises an annular monobloc housing defining twelve thermal compartments separated by seals and each receiving gadolinium in porous form. Each thermal compartment is provided with a minimum of four orifices, one inlet orifice and one outlet orifice connected to a hot circuit, and one inlet orifice and one outlet orifice connected to a cold circuit. The two permanent magnets are driven in continuous rotation so that they sweep the different thermal compartments while successively subjecting them to a magnetic field. The calories and/or frigories emitted by the thermal compartments are guided towards the heat exchangers by the hot and cold heat-transmitting circuits to which they are successively connected using several rotating seals which are connected in rotation by one or more belts to the continuous rotation axle of the two magnets. This heat generator simulates the operation of a liquid ring.
In order to operate, this heat generator requires continuous, synchronized, precise rotation by the different rotating seals and permanent magnets. The switching and sealing requirements associated with this rotation make this heat generator technically difficult and expensive to manufacture. Additionally, the principle of continuous operation severely limits this heat generator's perspectives of technical evolution.